Ill patients require surveillance of essential information relating to the patient's condition. Such information may relate to physiologic or anatomic functions or status. Apparatus which perform this surveillance function are referred to as monitoring systems. The most common signal employed for continuous surveillance is the electrocardiogram (ECG). Other physiologic functions that can be monitored include, but are not limited to temperature, blood pressure, respiration, blood oximetry, cardiac bio-impedance, and others. The system comprises an electronic monitor console connected to one or more cables, which terminate with a sensor device interfaced with the patient.
The most common location for the electronic monitor console is at the patient's bedside, but the patient may reside on a reclining chair, stretcher, gurney, operating-room table, or other similar modality, with the electronic monitor console similarly nearby. Often the patient can reach out and touch the electronic monitor console. One or more cables connect the electronic console to the patient to convey information from the patient. Such cables are most often electrical/electronic lines, but may also be pneumatic, hydraulic, or fiber-optic, consistent with the information being conveyed from patient to electronic console. Henceforth, in the description below, the term cable shall be broadly defined as the means of conveying such signals from the patient to the monitor console. Thus, the term cable could mean an electrical cable, a pneumatic cable, a fiber-optic cable, or other, depending on the application.
The modality that will be employed as the paradigm for initial description of a system configuration is the ECG, followed by analogous applications to temperature and blood pressure. The ECG is a wave-form depicting the time-varying difference in electrical potential between two points on the surface of the skin. Electrical connection to the skin is provided by a conductive electrode connected to a conductive wire; the simplest arrangement consists of the two active electrodes whose potential difference is to be measured, and a third electrode serving as a ground or reference electrode. This arrangement provides one ECG signal or lead; each additional lead requires an additional electrode with attached conductive wire. Since it is often desirable to monitor several ECG leads, it is common to have four or more electrodes with wires grouped as a packaged assembly.
To limit and control the transfer of infectious agents within the hospital environment, these electrodes with attached wires are frequently discarded after each patient use, since they are considered to be contaminated by the patient and not suitable for transfer to another ill individual. Being disposable, the electrode-wire assembly employs wires of minimal length which lie entirely on the patient or on his bed. Hereafter, we may refer to such wires as serial wires, since they are in series with the trunk cable, which then extends to the input connector of the electronic monitoring console. Thus, a bundled group of wires may constitute a cable and be denoted as the serial cable, so named as it is in series with the trunk cable. A connecting means, such as a metallic pin, located at the proximal end of each wire within the serial cable, couples to a multiple-input yoke at the distal end of a permanent trunk cable. Other connecting means may be possible. Of note, the terms proximal and distal are referenced to the electronic monitor console, proximal being closer to the console and distal being further away, in the direction of the patient.
The trunk cable extends all the way to the electronic monitor console to which it couples via a substantial multiple-conductor connector. Thus, the trunk cable contains multiple shielded wire conductors within its entire length and terminates in a multiple pin-receptive yoke at its distal end, and a substantial multiple-conductor connector at its proximal end, which is inserted into the input receptacle of the monitor console. Parenthetically, it is again noted that cables which are pneumatic, hydraulic, fiber-optic, or of a non-electronic nature will require respectively-appropriate connectors.
The trunk-cable is a relatively expensive component of the monitoring system and is not considered a disposable item, but is reused continuously through the sequence of patients to be interfaced with the monitor over time. The trunk-cable conspicuously reaches from the monitor console to the patient's bed, is contacted frequently by the patient, his bedclothes and linens, and is also handled frequently by caregivers at the patient's bedside. Thus, the trunk-cable is exposed directly to multiple sources of microbial contamination, and can transmit same to the subsequent sequence of patients for whom the monitoring system is employed.
Nosocomial infections are a major cause of in-hospital morbidity and responsible for large increases in hospital costs, for which reimbursement is not given. Hence, hospitals have intensely addressed causes of such hospital-acquired infection and have identified potential culprits. Among such sources of contamination and transmission of microbes are trunk-cables for ECG and trunk-cables for other monitored parameters, such as previously mentioned temperature, blood pressure, respiration, blood oximetry, bio-impedance, and others. Many hospitals attempt to reduce the virulence of trunk-cables by frequent wiping with anti-microbial disinfectants, but microbial cultures of trunk-cables have revealed such cleansing to be of limited value and not adequate for the objective. Hence, contamination of trunk cables remains a serious problem, contributing to the transmission of infective agents from one patient to another.